What I like to do to make the quilt larger is use up the scraps for sashings, borders or just to make it longer, I make small blocks of 4-patches or diamonds, flying geese, etc, then add a sash or 2, then the border. I make a lot of oversized lap quilts, especially making them longer to fit the person it's going to by adding those smaller blocks at the top and bottom before the sash and border.